Showing papers on "Equiaxed crystals published in 1996"
TL;DR: In this article, a multiscale/multiphase model for equiaxed dendritic solidification in the presence of melt convection and solid phase transport is proposed.
Abstract: Equiaxed dendritic solidification in the presence of melt convection and solid-phase transport is investigated in a series of three articles. In part I, a multiphase model is developed to predict com-position and structure evolution in an alloy solidifying with an equiaxed morphology. The model accounts for the transport phenomena occurring on the macroscopic (system) scale, as well as the grain nucleation and growth mechanisms taking place over various microscopic length scales. The present model generalizes a previous multiscale/multiphase model by including liquid melt convec-tion and solid-phase transport. The macroscopic transport equations for the solid and the interdendritic and extradendritic liquid phases are derived using the volume averaging technique and closed by supplementary relations to describe the interfacial transfer terms. In part II, a numerical application of the model to equiaxed dendritic solidification of an Al-Cu alloy in a rectangular cavity is dem-onstrated. Limited experimental validation of the model using a NH4C1-H2O transparent model alloy is provided in part III.
261 citations
01 Jan 1996-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, it was shown that GDRX occurs not only by recombination of opposite boundaries of the thinned grain, but also by pinching off of serrations.
Abstract: Geometric dynamic recrystallization (GDRX) is a process in which a refined and nearly equiaxed grain structure is formed, because grain boundaries which have become serrated during formation of subgrains in the course of hot deformation recombine as serrations pinch off or as the grains thin down. GDRX was first found in aluminium and more recently in AlMg solid solution. In the present work the question was addressed whether GDRX occurs also in an industrial Al alloy (5083) containing particles. Specimens were deformed in torsion from 473 to 773 K at equivalent (surface) strain rates between 10−3 and 4 s−1 to strains up to 3.6. Under these conditions the egg tray model predicts that GDRX will occur. This is indeed found from observations of the grain structure with light and electron microscopy. The results indicate that GDRX occurs not only by recombination of opposite boundaries of the thinned grain but also by pinching off of serrations. The size of the GDRX grains is about two to three times the subgrain size. The close similarity to Al5Mg means that the particles in the alloy do not prevent the small-scale grain boundary migration which is necessary to form the serrations. Static recrystallization after hot deformation destroys the DRX structure, if the specimen is not cooled fast enough.
149 citations
TL;DR: In this article, a numerical technique combining a fully implicit control-volume-based finite difference method with a multiple time-step scheme is developed for accurate and efficient simulations of both micro- and macroscale phenomena.
Abstract: The multiphase model developed in part I for equiaxed dendritic solidification with melt convection and solid-phase transport is applied to numerically predict structural and compositional development in an Al-4 wt pct Cu alloy solidifying in a rectangular cavity. A numerical technique combining a fully implicit control-volume-based finite difference method with a multiple time-step scheme is developed for accurate and efficient simulations of both micro- and macroscale phenomena. Quantitative results for the dendritic microstructure evolution in the presence of melt convection and solid movement are obtained. The remarkable effects of the solid-liquid multiphase flow pattern on macrosegregation as well as the grain size distribution are illustrated.
112 citations
TL;DR: In this paper, a multiphase model for equiaxed dendritic solidification is presented for the solidification of a NH4C1-70 wt pct H2O solution inside a square cavity cooled equally from all sidewalls.
Abstract: This third article on equiaxed dendritic solidification is intended to provide experimental validation of the multiphase model developed in part I. Numerical and experimental results are presented for the solidification of a NH4C1-70 wt pct H2O solution inside a square cavity cooled equally from all sidewalls. The numerical simulations were performed using the numerical procedures developed in part II. The experiments were conducted to measure the temperature historiesvia thermocouples and to record the images of the solidification process using a shadowgraph system. Preliminary validity of the multiphase model is demonstrated by the qualitative agreement between the measurements and predictions of cooling curves as well as of the evolution of the crystal sediment bed. In addition, several important features of equiaxed dendritic solidification are identified through this combined experimental and numerical study, including the grain generation and growth behaviors in the presence of liquid flow, the sedimentation of equiaxed crystals, the formation of a crystal sediment bed, and a bottom zone of negative segregation resulting from the countercurrent solid-liquid multiphase flow. Quantitative comparisons between the numerical simulation and experiment reveal several areas for future research.
94 citations
TL;DR: In this article, the evolution of the microstructure is governed by the diffusion of boron and carbon, rather than titanium, which is an intermediate phase in the platelet composition and appears to be important to the development of the Ti3B4 phase.
Abstract: Transient plastic phase processing is a form of reactive hot pressing for fabricating fully dense ceramic-ceramic composites at relative low homologous temperatures. In this study, this technique has been used on two powder mixtures—4:1 Ti/B4C and 1:1 TiC0.5/TiB2, which are equivalent in terms of elemental compositions—to produce fully dense titanium carbide-titanium boride composites. The composites formed in each case are comprised of the same final phases—TiCx, TiB2, and Ti3B4, in roughly the same volume fractions—but exhibit distinctly different grain morphologies. Ti3B4 phase nucleates and grows as platelets for the 4:1 Ti/B4C starting composition but as equiaxed grains for the 1:1 TiC0.5/TiB2 composition. TiB has been identified as an intermediate phase in the “platelet” composition and appears to be important to the development of the Ti3B4 platelets. X-ray diffractometry and scanning electron microscopy results indicate that the evolution of the microstructure is governed by the diffusion of boron and carbon, rather than titanium. In addition, the faster diffusion of carbon, relative to boron, is instrumental in the microstructural evolution of the platelet composite. The produced composites possess >99% density and good mechanical properties. The higher strength and toughness of the platelet composite are believed to be due to the platelet morphology of the Ti3B4 phase.
88 citations
TL;DR: In this article, the microstructures of the adiabatic shear band (ASB) on the pure titanium side in the titanium/mild steel explosive cladding interface were investigated by means of OM, SEM and TEM.
84 citations
TL;DR: In this paper, a platelet-based reaction-sintered alumina composite was evaluated using the indentation strength in bending technique, and a simple grain pullout model was used to estimate the toughening increment due to bridging by the platelet grains; the value obtained was in good agreement with toughness curves derived from indentation-strength measurements.
Abstract: The mechanical behavior of reaction-sintered alumina: 30 vol% calcium hexaluminate (Al2O3:CaAl12O19,or A12O3: CA6) composites was evaluated using the indentation strength in bending technique. A composite in which the hexaluminate (CA6) phase possessed a platelike morphology showed more-pronounced R-curve behavior than a composite in which the CA6 phase consisted of equiaxed grains. Toughness curves derived from the indentation-strength data exhibited a “crossover,” such that the platelet composite exhibited the lower toughness at small flaw sizes, but the higher toughness at large flaw sizes. Incorporation of the platelet CA6 resulted in enhanced toughening, compared to single-phase alumina of comparable grain size, thus demonstrating the viability of the in-situ-toughening approach. A simple grain-pullout model was used to estimate the toughening increment due to bridging by the platelet grains; the value obtained was in good agreement with toughness curves derived from indentation-strength measurements. Finally, fabrication of trilayer specimens, whereby outer layers of equiaxed A12O3:CA6 composite were strongly bonded to the platelet A12O3:CA6 composite, demonstrated high strength over the range of tested flaw sizes.
82 citations
15 Oct 1996-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: A submicrometer-grained (SMG) microstructure, with an average grain size of ∼0.2 μm, was introduced into an Al-3% Mg solid solution alloy by equal-channel angular pressing as mentioned in this paper.
Abstract: A submicrometer-grained (SMG) microstructure, with an average grain size of ∼0.2 μm, was introduced into an Al-3% Mg solid solution alloy by equal-channel angular pressing. The SMG structure was heterogeneous with regions of equiaxed and elongated grains and with grain boundaries in a non-equilibrium configuration. Samples were annealed for various times at a temperature of 473 K and then examined using transmission electron microscopy. The results show that the grain boundaries evolve with time into an equilibrium condition and some limited grain growth occurs primarily in the grains where recovery has taken place. The results establish that the SMG structure is reasonably stable in the Al-3% Mg alloy at a temperature of 473 K.
77 citations
TL;DR: In this paper, the role of solute concentration on equiaxed crystal growth mechanisms and grain size has been investigated and it was found that two principally different growth models have to be applied in different parts of an alloy system.
Abstract: The role of solute concentration on equiaxed crystal growth mechanisms and grain size has been investigated. The study was undertaken on hypoeutectic concentrations in the systems Al-Si-Ti and Al-Si-Fe-Ti. The equiaxed structure was ensured by adding heterogeneously nucleating TiB{sub 2} particles in excess of that needed for a maximum grain-refining effect. It was found that two principally different growth models have to be applied in different parts of an alloy system. Cellular type of crystals in the low alloy region develop in a clover-leaf form and the diffusion profile build up front-wise ahead of the cellular interface. The alloying elements cooperate by growth restriction in promoting a fine-grained structure. On the high alloy side, however, dendrites with orthogonal branches develop lancet-like tips causing a major part of the diffusion to take place side-wise instead of in front of the growing tip. Increasing the solute concentration in this regime will increase the growth rate and consequently the grain size. (orig.)
67 citations
TL;DR: In this article, an analysis of the transition from growth-controlled to nucleation-controlled microstructure development has been formulated based upon the limiting solidification interface temperature at the transition and a heterogeneous volume nucleation model.
66 citations
TL;DR: The unified theory for elastic wave propagation in polycrystalline materials, developed by Stanke and Kino as mentioned in this paper, has been applied to compute the propagation constants in materials consisting of cubic crystallites with texture.
Abstract: The unified theory for elastic wave propagation in polycrystalline materials, developed by Stanke and Kino [J. Acoust. Soc. Am. 75, 665–681 (1984)], has been applied to compute the propagation constants in materials consisting of cubic crystallites with texture. The particular texture considered here is one in which one of the cube axes of each crystallite is aligned in a preferred direction with the other two being randomly oriented, leading to a material with macroscopic transverse isotropy. The calculations are done for plane waves under the assumption that the single crystal anisotropy is not large. Numerical results for the variations of attenuation and phase velocity with direction of propagation and frequency are presented for L, SH, and SV waves.
Journal Article•
TL;DR: In this paper, the influence of phase fractions on the development of hot rolling textures of the α and β phases of titanium alloys has been investigated and a comparison of the experimental and theoretical rolling textures leads to a well founded description of the occurring slip mechanisms and also to a critical assessment of the used model.
Abstract: In two-phase titanium alloys, the influence of the phase fractions on the development of the hot rolling textures of the {alpha} and {beta} phase are investigated. Therefore, specimens with equiaxed microstructure are rolled in one path ({epsilon}=1.2) and subsequently water quenched. By this procedure effects of recrystallization are minimized. From the textures of the room temperature phases the genuine rolling textures are reconstructed. These vary strongly with the phase fractions. They are presented by orientation distribution functions and analysed by the help of computational modelling on the basis of a viscoplastic self-consistent model. The comparison of the experimental and theoretical rolling textures leads to a well founded description of the occurring slip mechanisms and also to a critical assessment of the used model. (orig.)
TL;DR: In this paper, single crystals of CrB, Cr3B4, Cr2B3, and CrB2 were obtained as columnar and thick platelet crystals having well-developed (010) and (100) faces with maximum dimensions of 3 to 8 mm.
TL;DR: The mechanical properties of commercially pure (CP) titanium can be improved by controlled additions of the interstitial elements oxygen (O), nitrogen (N), and carbon (C) as well as iron without sacrificing ductility as discussed by the authors.
TL;DR: In this paper, an analytical model that describes solidification of equiaxed dendrites has been developed for use in solidification kinetics-macrotransport modeling.
Abstract: An analytical model that describes solidification of equiaxed dendrites has been developed for use in solidification kinetics-macrotransport modeling. It relaxes some of the assumptions made in previous models, such as the Dustin-Kurz, Rappaz-Thevoz, and Kanetkar-Stefanescu models. It is assumed that nuclei grow as unperturbed spheres until the radius of the sphere becomes larger than the minimum radius of instability. Then, growth of the dendrites is related to morphological instability and is calculated as a function of melt undercooling around the dendrite tips, which is controlled by the bulk temperature and the intrinsic volume average concentration of the liquid phase. When the general morphology of equiaxed dendrites is considered, the evolution of the fraction of solid is related to the interdendritic branching and dynamic coarsening (through the evolution of the specific interfacial areas) and to the topology and movement of the dendrite envelope (through the tip growth velocity and dendrite shape factor). The particular case of this model is the model for globulitic dendrite. The intrinsic volume average liquid concentration and bulk temperature are obtained from an overall solute and thermal balance around a growing equiaxed dendritic grain within a spherical closed system. Overall solute balance in the integral form is obtained by a complete analytical solution of the diffusion field in both liquid and solid phases. The bulk temperature is obtained from the solution of the macrotrasport-solidification kinetics problem.
Patent•
13 Nov 1996TL;DR: In this article, a process for simultaneously improving at least two mechanical properties of mill-processed (α + β) titanium alloy, which may or may not contain silicon, is described.
Abstract: The invention is a process for simultaneously improving at least two mechanical properties of mill-processed (α + β) titanium alloy, which may or may not contain silicon, which includes steps of heat treating the mill-procesed titanium alloy such that the (α + β) microstructure of said alloy is transformed into an (α + α2 + β) microstructure, preferably containing no silicides. The heat treating steps involve subjecting the mill-processed titanium alloy to a sequence of thermomechanical process steps, and the mechanical properties which are simultaneously improved include (a) tensile strength at room, cryogenic, and elevated temperatures; (b) fracture toughness; (c) creep resistance; (d) elastic stiffness; (e) thermal stability; (f) hydrogen embrittlement resistance; (g) fatigue; and (h) cryogenic temperature embrittlement resistance. As a consequence of the process, the (α + α2 + β) microstructure contains equiaxed alpha phase strengthened with α2 precipitates coexisting with lamellar alpha-beta phase, where the α2 precipitates are confined totally to the equiaxed primary alpha phase. The invention also encompasses a composition of matter produced by the inventive process, especially one comprising a titanium alloy having an (α + α2 + β) microstructure.
TL;DR: In this paper, a new analytical model that describes solidification of equiaxed dendrites was presented, which was incorporated into a commercial finite-element code, PROCAST.
Abstract: In Part I of the article, a new analytical model that describes solidification of equiaxed dendrites was presented. In this part of the article, the model is used to simulate the solidification of INCONEL 718 superalloy castings. The model was incorporated into a commercial finite-element code, PROCAST. A special procedure called microlatent heat method (MLHM) was used for coupling between macroscopic heat flow and microscopic growth kinetics. A criterion for time-stepping selection in microscopic modeling has been derived in conjunction with MLHM. Reductions in computational (CPU) time up to 90 pct over the classic latent heat method were found by adopting this coupling. Validation of the model was performed against experimental data for an INCONEL 718 superalloy casting. In the present calculations, the model for globulitic dendrite was used. The evolution of fraction of solid calculated with the present model was compared with Scheil’s model and experiments. An important feature in solidification of INCONEL 718 is the detrimental Laves phase. Laves phase content is directly related to the intensity of microsegregation of niobium, which is very sensitive to the evolution of the fraction of solid. It was found that there is a critical cooling rate at which the amount of Laves phase is maximum. The critical cooling rate is not a function of material parameters (diffusivity, partition coefficient,etc.). It depends only on the grain size and solidification time. The predictions generated with the present model are shown to agree very well with experiments.
TL;DR: In this paper, the microstructure of the reaction layer comprises titanium aluminide particles dispersed in an Al rich matrix, and morphological features of the particles have been shown to be widely differing with the reaction conditions.
Abstract: Microstructural evolution in TiAl3 and TiAl3 base alloys formed by the reaction synthesis between liquid Al and solid Ti or Ti alloys has been studied by carrying out the tests on reaction couples isothermally reacted between 973 and 1373 K for different time intervals It has been found that the reaction product forms by the exothermic chemical reaction and while TiAl3 is the only reaction product formed up to the reaction tempperature of 1273 K, TiAl3 as well as Ti9Al23 form when the reaction is carried out at 1373 K In all cases the microstructure of the reaction layer comprises titanium aluminide particles dispersed in an Al rich matrix However, morphological features of titanium aluminide particles been shown to be widely differing with the reaction conditions In pure Ti-Al reaction couples an increase in the reaction temperature from 973 to 1173 K leads to the formation of particles having a bi-modal distribution At the reaction temperature of 1173 K a large number of particles formed contain several micro-cracks In contrast to TiAl3 formed in the case of pure Ti-Al couples, the morphology of the TiAl3 based compounds containing V or Mo, Zr and Si has been found to be significantly different Instead of being equiaxed, the particles of TiAl3 based compounds have a continuously changing morphology across the reaction layer The particles away from the reaction interface, in general, are not equiaxed, and have sharp edges and many of them have severe internal micro-cracks
Patent•
24 Jul 1996TL;DR: The alloys of the α+β type have a microstructure consisting of any of an acicular α-phase consisting of α-crystals having a width of not smaller than 1 μm and dispersed with equiaxed α crystals as discussed by the authors.
Abstract: Bars of titanium alloys suited for the manufacture of at least the stems (2), (3) of engine valves are mass-producible while maintaining good configurational and dimensional accuracies throughout the valve fabricating process and the wear-resistance imparting processes to at least the stems (2), (3), by surface oxidizing and nitriding. The alloys are of the α+β type whose microstructure consists of any of an acicular α-phase consisting of acicular α crystals having a width of not smaller than 1 μm, an acicular α-phase consisting of acicular α crystals having a width of not smaller than 1 μm and dispersed with equiaxed α crystals, and an equiaxed α-phase consisting of α crystals whose diameter is not smaller than 6 μm. Their microstructure may also include one in which the diameter of the pre-β crystals in the acicular α-phase is not larger than 300 μm and the width of the acicular α crystals is not smaller than 1 μm and not larger than 4 μm. Selection of these alloys assures very efficient manufacture.
TL;DR: In this article, the authors investigated the fatigue crack growth behavior of binary and chromium/niobium alloyed γ-base titanium aluminides with lamellar, duplex and equiaxed microstructures.
TL;DR: In this article, a spray forming with mush uniform-droplets deposited onto a solidified deposit surface produced a fine, equiaxed microstructure in a Sn-5wt.%Pb alloy.
TL;DR: The microstructure of laser-clad 60 vol.% ZrO2 plus 40 vol.%. Ni alloy composite coating on steel 1045 was investigated by scanning electron microscopy, electron probe microanalysis, X-ray diffraction, energy-dispersive Xray analysis and microhardness tests.
Abstract: The microstructure of laser-clad 60 vol.% ZrO2 (partially stabilized with 2 mol% Y2O3) plus 40 vol.% Ni alloy composite coating on steel 1045 was investigated by scanning electron microscopy, electron probe microanalysis, X-ray diffraction, energy-dispersive X-ray analysis and microhardness tests. The composite coating consists of a pure ZrO2 clad layer in the outer region and a bonding zone of Ni alloy adjacent to the substrate. The pure ceramic layer exhibits fine equiaxed ZrO2 grains in the outer zone and columnar ZrO2 dendrites in the inner zone, growing from the ceramic layer-bonding zone interface. This ceramic layer is composed of metastable t′-ZrO2 phase and a very small amount of m-ZrO2 phase and displays a microhardness of 1700 HV0.2. The high heating and cooling rate caused by laser cladding restrains the t → m phase transformation in the ZrO2 ceramic layer. Interdiffusion of alloy elements takes place in the bonding zone, in which the coexistence of ZrO2 particles, Ni-based solid solution and (Fe,Cr)23C6 particles in the interdendritic regions was found.
Patent•
24 May 1996
TL;DR: An unwrought continuous cast Cu-Ni-Sn spinodal alloy and a method for producing the same is disclosed in this paper, which is characterized by an absence of discontinuous η' phase precipitate at the grain boundaries, ductile fracture behavior during tensile testing, high strength, excellent wear and corrosion resistance, superior bearing properties, and contains from about 8-16 wt% nickel, from about 5-8 wt % tin, and a remainder copper.
Abstract: An unwrought continuous cast Cu-Ni-Sn spinodal alloy and a method for producing the same is disclosed The Cu-Ni-Sn spinodal alloy is characterized by an absence of discontinuous η' phase precipitate at the grain boundaries, ductile fracture behavior during tensile testing, high strength, excellent wear and corrosion resistance, superior bearing properties, and contains from about 8-16 wt% nickel, from about 5-8 wt% tin, and a remainder copper As a method for producing the spinodal alloy, a continuous cast Cu-Ni-Sn billet, hollow billet, or rod composed of small, equiaxed crystals is subjected to solution heat treatment and aging steps to effect spinodal decomposition type phase transformation According to our invention, it is not necessary to subject the cast rod, billet or casting to wrought processing prior to the spinodal decomposition heat treatment in order to obtain a strong and ductile material, thereby allowing for the use of the unwrought continous cast Cu-Ni-Sn spinodal alloy in the manufacture of various components which heretofore have been manufactured from materials other than an unwrought Cu-Ni-Sn spinodal alloy
TL;DR: A 2H-solid solution between SiC and AlN, along with a dispersion of SiC, was prepared by liquid-phase sintering, and the mechanism of solid solution formation was investigated from studies of the microstructures of the sintered body as mentioned in this paper.
15 Jul 1996-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the microstructural evolution of a Cu-15wt.% in situ metal matrix composite has been investigated by means of scanning electron microscopy, analytical transmission electron microscope, high resolution electron microscope and energy-dispersive X-ray spectrometry.
Abstract: The microstructural evolution of a Cu-15wt.%Cr in situ metal matrix composite has been investigated by means of scanning electron microscopy, analytical transmission electron microscopy, high resolution electron microscopy and energy-dispersive X-ray spectrometry. It is found that the dendritic Cr and equiaxed Cr in the as-cast state are mostly deformed into Cr ribbons after cold rolling to 89.8% reduction in thickness. In these heavily deformed Cr ribbons, ellipsoidal Cu-rich clusters with size around 1 nm were observed which have the same lattice as the Cr ribbons but different Cu concentrations from each other. Lattice distortion also exists around these Cu-rich clusters, though its extent varies depending on the Cu concentration in each cluster.
TL;DR: In this paper, the microstructures of bulk Ge and Cu samples solidified from undercooled liquid were investigated and the structural transformation in the two materials was analyzed with respect to the relation between undercooling and the velocity of free crystal growth, twinning mechanisms and a dendrite break-up model.
TL;DR: In this article, a wrought two-phase γ-titanium aluminide alloy Ti-45.5Al-2Nb-2Cr containing a fine, equiaxed microstructure was investigated with special reference to the influence of temperature transients immediately preceding plastic deformation.
Abstract: The hot deformation behavior, microstructure development, and fracture characteristics of a wrought two-phase γ-titanium aluminide alloy Ti-45.5Al-2Nb-2Cr containing a fine, equiaxed microstructure were investigated with special reference to the influence of temperature transients immediately pre-ceding plastic deformation. Specimens were soaked at 1321 °C or 1260 °C, cooled directly to test temperatures of 1177 °C and 1093 °C, and upset under conditions of constant strain rate and tem-perature. Plastic flow behavior and microstructure evolution occurring in tests involving prior tem-perature transients were compared with those occurring in specimens which were directly heated to the test temperature and upset under identical deformation conditions. Flow curves associated with prior exposure at 1321 °C exhibited very sharp peaks and strong flow softening trends compared to those obtained under isothermal conditions,i.e., involving no temperature transients. During cooling from 1321 °C, the metastable α phase undergoes limited or complete decomposition into α/α2 + γ lamellae, depending on the final temperature (1177 °C/1093 °C). Subsequent hot deformation leads to partial globularization of the lamellae together with extensive kinking and reorientation of lamellae. In contrast, isothermal deformation at 1177 °C/1093 °C preserves the fine, equiaxed microstructure, through dynamic recrystallization of the γ grains. Cracking observed in specimens deformed at 1093 °C and 1.0 s−1 after exposure at 1321 °C has been attributed to the low rate of globularization as well as the occurrence of shear localization. Plastic flow behavior observed in this work is compared with that observed in several single-phase and two-phase gamma titanium aluminide alloys in order to identify mechanism(s) responsible for flow softening.
TL;DR: In this article, the microstructural properties have been investigated for titanium-aluminide (Ti-53mol%Al) compacts spark sintered at four temperatures: 1573, 1623, 1648, and 1673 K after pulsed electrical discharge.
TL;DR: In this article, a novel technique known as combustion assisted synthesis was utilised for the fabrication of titanium carbide + titanium boride reinforced titanium matrix composites, which resulted in a homogeneous distribution of rod like (TiB) and equiaxed (Ti2C) reinforcements in a fine grained (1-2 μm) titanium matrix, with a clean matrix/particle interface.
Abstract: A novel technique known as combustion assisted synthesis was utilised for the fabrication of titanium carbide + titanium boride reinforced titanium matrix composites. This technique resulted in a homogeneous distribution of rod like (TiB) and equiaxed (Ti2C) reinforcements in a fine grained (1–2 μm) titanium matrix, with a clean matrix/particle interface. The deformation behaviour of the composites and the control sample of titanium were studied in the temperature range 298–873 K and strain rate range 2 × 10−5−2 × 10−2s−1. Tests indicated that the composites were more deformable in compression and the values of yield strength of the composites increased with volume fraction of reinforcements, being approximately × 3–5 that of the control titanium. Fractographic analysis indicated that the composites failed in tension due to particle cracking, whereas the failure mode of the control titanium was dimpled fracture.MST/3255